After graduating from medical school he spent a year as a fellow in the Department of Psychiatry, Emory University studying arrested alcoholics in the city jail in Atlanta.[2] He established a ground-breaking program through which arrested alcoholics could take the drug antabuse as an alternative to serving prison time.[3] He was active in the Civil Rights movement and participated in the effort to integrate lunch counters in the city. In 1963–64 he was a rotating intern, Kings County Hospital, Seattle.

After returning from Vietnam he was active in the anti-war movement. Upon discharge from the Army he completed a residency in psychiatry at Stanford University, California. During this period he also worked as a volunteer in the Haight-Ashbury Free Medical Clinic.

In 1969 he returned to Emory University, Atlanta as an Assistant Professor of Psychiatry, and Community Health. He ran the mental health department of a Federally funded Community Health Center which he eventually expanded into a free standing community mental health center-the first in Georgia. He continued to play an active role in the integration efforts in Georgia and the South. Together with his first wife, Judith Rooks, Bourne led an effort to overturn Georgia's restrictive abortion laws. Having failed in the State legislature, together with other plaintiffs, they filed suit against the state on behalf of Jane Doe, a patient seeking an abortion for whom Bourne was the physician of record. Following victories for the plaintiffs in the state courts the case, as Doe vs Bolton, was appealed to the Supreme Court of the US. It was heard together with the better known case from Texas, Roe vs Wade. The court's watershed ruling based on the two cases transformed women's access to abortion in the US.[5] He was active with the American Psychiatric Association (APA), chairing the organization's Task Force on Drugs and Drug Abuse Education and serving on the Task Force on the Treatment of Psychiatric Disorders. He has served on the editorial board of the journal Psychiatry since 1969. In 2008 he was made a Distinguished Life Fellow of the APA. In 1972 he was named one of "The Five Outstanding Young Men in Georgia".

Bourne had run, as part of his mental health center, a treatment program for heroin addicts. As a result he was appointed by the newly elected Governor of Georgia, Jimmy Carterto set up Georgia's first statewide drug treatment program. Bourne was personally close to Carter and was influential in convincing him to run for the Presidency[6] He would later become a key strategist and deputy campaign campaign director for Carter running the Washington office for the successful 1976 presidential campaign.

As a result of setting up and successfully running Georgia's first statewide drug treatment program, Bourne was asked to take a position as Assistant Director in charge of treatment programs in President Nixon's Special Action Office of Drug Abuse Prevention (SAODAP) in Washington. Bourne did so with the intention of resigning as soon as Carter announced his plans to run for the presidency. After leaving the administration he became a fellow at the Foundation-supported Drug Abuse Council and was also made a member of the faculty at Harvard Medical School with a clinical appointment at McLean Hospital in Boston. He was also a consultant to the World Health Organization, and the UN Commission on Narcotic Drugs. After Carter announced his plans for the presidency Bourne established and directed the Campaign office in Washington which gradually became a full-time activity.

Under Jimmy Carter, Bourne was appointed special assistant to the President for health issues and Director of the Office of Drug Abuse Policy (ODAP). He resigned this position on July 20, 1978, amid controversy concerning his efforts to maintain the confidentiality of one of his staff for whom he had written a prescription. Under his leadership, however, the number of deaths from drug overdoses dropped to its lowest level in 30 years. Bourne served as the personal envoy of the President of the United States in bilateral discussions with heads of state or government in Burma, Colombia, Thailand, the Philippines and Jamaica. He chaired the World Hunger Working Group, a sub-cabinet committee formed to formulate new US policy with regard to world hunger.[7] This led to the establishment of the Presidential Commission on World Hunger and Malnutrition. He also chaired the Interagency Committee on World Health formed to review the US role in global health and to formulate new presidential initiatives in this area.[8] He was the White House coordinator for the Presidential Commission on the UN International Year of the Child, and with Rosalynn Carter established a Commission on Mental Health and Mental Illness. Bourne also served on the President's Commission on White House Fellows.

Bourne was made the White House Coordinator for International Human Needs (health, literacy, housing, family planning and disaster relief) and the liaison with the UN specialized. In that capacity he was a member of the US delegation to the Executive Committee of UNICEF, Manila (1977), a member of the US delegation to the World Health Assembly, Geneva 1977,1978, a member of the US delegation to the UN Commission on Narcotic Drugs, Geneva 1977, 1978, and Chairman of the US Delegation to the Governing Council of UN Development Programme (UNDP), Geneva, 1978.

In 1979, Bourne became an Assistant Secretary-General at the United Nations, where he established and ran the "International Drinking Water and Sanitation Decade," a 10-year program that would provide clean drinking water to more than 500 million people worldwide. As part of the program Bourne launched, in collaboration with the Centers for Disease Control and Prevention, a global campaign to eradicate the water borne disease caused by guinea worm. Eventually he convinced former president Carter to become the public face of the campaign which is now nearing complete success.[9]

After leaving the UN in 1982 for the private sector, Bourne established an NGO, Global Water, to pursue the same goals as the UN program. He began serving on the boards of numerous charities including Save the Children, The Hunger Project (Chairman of the Board, 1998–2009), Health and Development International, International Health Society, Student Partnerships Worldwide (SPW), the American Association for World Health (Chairman of the Board), American Public Health Association, The Institute for Human Virology (IHV), Royal Society of Medicine (fellow), the Center for Genetics Nutrition and Health and the Jefferson Awards for Public Service. Bourne also served on the Jury of the prestigious medical prize, The Lasker Awards. He also became president of Tropica Development Ltd, a company involved in fostering economic programs in Africa.

Building on a long standing interest in the Cuban health care system and relationships established during several visits to the country when in the White House and at the UN Bourne published in 1986 a well received biography of Fidel Castro.[10] In 1995 as chairman of the American Association for World Health he directed a year-long foundation-supported study of the impact of the US embargo on health and nutrition in CubaDenial of Food and Medicine: The Impact of the US Embargo on Health and Nutrition in Cuba. He co-authored the subsequent report.[11] The study, translated into six languages, drew worldwide attention and lead to the establishment of the NGO, Medical Education Cooperation with Cuba (MEDICC)[12] Its initial objective was to enable senior US medical students to spend six week electives with family doctors in Cuba. Over five years more than 1,500 students from virtually every medical school in the U.S. took advantage of this program. In 2004 Federal regulations with regard to Cuba were changed making impossible to continue this student program. MEDICC then focussed on the production of a movie on the Cuban health system,[13] the publication of a peer-reviewed, English language journal on Cuban health and medicine[14] and the recruitment of delegations of high level health policy makers to visit Cuba.

Beginning in 1980 Bourne had been, on a part-time basis, chairman of the Department of Psychiatry at St. George's University Medical School in Grenada involving the placement and supervision of medical students in psychiatric teaching hospitals in the USA and the UK. In 1998 he moved to Grenada, West Indies, and became Vice Chancellor of St. George's University.[16] Over the next five years he built and enhanced the reputation of the medical school, established a school of veterinary medicine, grew the embryonic school of arts and sciences into the second largest institution in the region for students of Caribbean origin, opened a program in public health granting an MPH degree, and started a department of marine biology. He also launched on campus, in collaboration with the West Indies Cricket Board, The Shell Cricket as the main training institution for the West Indies cricket team. It gave the university, for the first time, recognition and acceptance throughout the English-speaking Caribbean.

In 2003 Bourne left Grenada and returned to Washington, D.C. He was appointed as a Visiting Senior Research Fellow at Green Templeton College at the University of Oxford [1] and began dividing his time between the US and the UK. This included increasing the time he spent at his farm in Wales where he raised red deer, llamas and North American bison. In 2012 he was made a Visiting Distinguished Fellow at the Rothermere American Institute of Oxford University. At Green Templeton College he was on the steering committee of the annual Emerging Markets Symposium.[1]

Bourne is a member of the Reform Club (London), the Special Forces Club (London), and a Fellow of the Royal Society of Medicine. He is listed in Who's Who in America, Who's Who in American Politics, and American Men and Women of Science. A recreational runner he was, in 1993, Nationally Ranked in the marathon for his age group (age 44yrs) after completing the Marine Corps marathon in 2 hours, 45 min, 14 secs. At age 73 years he came in first in the over 70 category in the Oxford Half-Marathon. He also has a private pilot's license.